I think I've worked all the serious bugs out of the CP5.6.2AN, so as of this afternoon, my perl 5.6.2 testing machine is using http://cp5.6.2an.barnyard.co.uk/ as its CPAN mirror. It is a BackPAN with a custom 02packages file which lists the modules in the latest version of each distribution to have a PASS result in the CPAN-testers database for perl 5.6.2.
Because it's an up-to-date backpan I can still ask it for things like A/AU/AUTHOR/New-Dist-1.0.tar.gz and test them (even if there's no passes in the database, so no entries in the index), but when the Build.PL or Makefile.PL specifies Some::Module as a dependency, it will look in the index and find a version of that module that works on the perl I'm testing with, so even if the most recent version of Some::Module doesn't work on 5.6.2, I can still test to see whether New-Dist does. Hurrah!
There's also a version for perl 5.8.8, and I can very quickly add other versions on request.
Both sites update shortly after 6am every morning, and source code is available here. If you would like to clone my git repo, email me to ask for the username/password.
The aim of this project is to minimise the pain if for some reason you are stuck on an old version of perl. This includes 5.8.x, as there are now modules where the latest version only works on perl 5.10.